This invention relates generally to the field of cataract surgery and more particularly to a method and apparatus for bi-manual phacoemulsification surgery.
The human eye in its simplest terms functions to provide vision by transmitting light through a clear outer portion called the cornea, and focusing the image by way of the lens onto the retina. The quality of the focused image depends on many factors including the size and shape of the eye, and the transparency of the cornea and lens.
When age or disease causes the lens to become less transparent, vision deteriorates because of the diminished light that can be transmitted to the retina. This deficiency in the lens of the eye is medically known as a cataract. An accepted treatment for this condition is surgical removal of the lens and replacement of the lens function by an artificial intraocular lens (IOL).
In the United States, the majority of cataractous lenses are removed by a surgical technique called phacoemulsification. A typical surgical handpiece suitable for phacoemulsification procedures consists of an ultrasonically driven handpiece, an attached cutting tip, and irrigating sleeve and an electronic control console. The handpiece assembly is attached to the control console by an electric cable and flexible tubings. Through the electric cable, the console varies the power level transmitted by the handpiece to the attached cutting tip and the flexible tubings supply irrigation fluid to and draw aspiration fluid from the eye through the handpiece assembly.
The operative part of the handpiece is a centrally located, hollow resonating bar or horn directly attached to a set of piezoelectric crystals. The crystals supply the required ultrasonic vibration needed to drive both the horn and the attached cutting tip during phacoemulsification and are controlled by the console. The crystal/horn assembly is suspended within the hollow body or shell of the handpiece by flexible mountings. The handpiece body terminates in a reduced diameter portion or nosecone at the body's distal end. The nosecone is externally threaded to accept the irrigation sleeve. Likewise, the horn bore is internally threaded at its distal end to receive the external threads of the cutting tip. The irrigation sleeve also has an internally threaded bore that is screwed onto the external threads of the nosecone. The cutting tip is adjusted so that the tip projects only a predetermined amount past the open end of the irrigating sleeve.
A modified phacoemulsification technique called “bimanual” phacoemulsification has been adopted by many surgeons. With the bimanual technique, the irrigation sleeve is removed from around the ultrasonically drive tip. This allows for the small tip to be inserted into the eye through a smaller incision. Irrigation fluid is supplied by a second irrigating tip. Additional information concerning traditional phacoemulsification and bimanual phacoemulsification is included in U.S. Patent Publication No. US 2003/0004455 A1. And in particular, Paragraphs [0001] through [0008], which are incorporated herein by reference. As described in this reference, traditional phacoemulsification tips/irrigation sleeves have a larger overall diameter, requiring a larger incision. Traditional phacoemulsification tips/irrigation sleeves are also described as causing “roiling” in the area immediately in front of the phaco tip, and visibility-reducing “clouding” of debris. According to this reference, a bi-manual technique solves these and other problems. In the bimanual technique, the incision may be smaller because the irrigation sleeve on the ultrasonic tip is not used, but without the sleeve, there is direct contact between the vibrating tip and the tissue at the wound. This can result in extra stress on the wound tissue, delaying healing and possibly requiring the use of a suture to seal the wound at the completion of surgery. The soft irrigation sleeve also acts to seal the wound from leakage during surgery. Without the use of the irrigation sleeve, excessive wound leakage can cause shallowing of the anterior chamber, excessive turbulence and premature removal of the protective viscoelastic material. Excessive wound leakage can also cause over-hydration of the wound tissue, possibly resulting in edema.
Therefore, a need continues to exist for a method and device for conducting phacoemulsification through a small incision.